18
During commissioning it is recommend that initially
the second digit is set to 0 (off) and the first digit is
adjusted to provide acceptable rate display
stability. The second digit should then be
increased until the selected step size is greater
than the noise on the display signal, at which
setting the rate display will again become stable.
These will be the optimum filter parameters for
acceptable rate display stability and a fast
response to a large rate signal change.
To check or change the filter select 'FILtEr' from
the main menu and press P to reveal the current
settings. Pressing the Up or Down button will
change the flashing digit and P will transfer control
to the second digit. While making adjustments the
filtered rate display is shown on the lower display
so that stability can be assessed. When set as
required, press the E button to enter the revised
parameters and return to the main menu.
6.11 Total scale factor: ‘SCALE-t’
This factor defines the arithmetic relationship
between the number of input pulses and the total
display. SCALE-t is a dividing factor that may be
adjusted between 0.001 and 99999999. See Fig
8.
When used with a flowmeter SCALE-t should be
set to the K-factor of the flowmeter i.e. the number
of pulses the flowmeter produces for a unit of flow.
If the BA338C total display is required in units
different from those in which the flowmeter K factor
is specified, a conversion factor will be required.
e.g. If the flowmeter has a K factor of 45.6 pulses
per litre and the BA338C total display is required in
units of 1,000 gallons, then SCALE-t should be set
to number of pulses produced by the flowmeter per
1,000 gallons:
45.6 x 4.54609 x 1000
207,301.7 pulses per 1000 gallons
.
(there are 4.54609 litres in a UK gallon)
To check or change the total scale factor select
'SCALE-t' from the main menu and press P to
reveal the existing setting, one digit will be
flashing. The value of the flashing digit can be
changed by pressing the Up or Down buttons.
When this digit is correct pressing P will transfer
control to the next digit.
To position the decimal point in the scaling factor,
move the flashing digit to the left hand side of the
required decimal point position and simultaneously
press the Up and Down buttons.
When the required total scale factor has been
entered, press E to store the number and return to
the main menu.
6.12 Clip-off: ‘CLIP-OFF’
To prevent totalisation of very low flow rates that
over long periods may result in significant
totalisation errors, the BA338C may be
programmed to stop totalising when the flow rate
falls below an adjustable threshold.
To check or change the clip-off threshold select
'CLIP-OFF' from the main menu and press P which
will reveal the current setting. The threshold is
shown in the units already selected for the flow
rate display. One digit will be flashing. The value
of the flashing digit may be changed by pressing
the Up or Down buttons. When this digit is correct
pressing P will transfer control to the next digit.
When clip-off is set as required, press the E button
to enter the revised figure and return to the main
programme menu.
If the flow rate falls below the entered threshold,
the rate display will show zero flow, totalisation will
stop and the HOLD annunciator will be activated.
The flow indicator will rotate for 2 seconds each
time an input pulse is received i.e. at input
frequencies above 0.5Hz it will appear to rotate
continuously.
Note:
When the rate scale factor SCALE-r, the
timebase t-bASE, or the position of the rate
display
decimal point are changed, clip-off will
automatically be reset to zero. If required, a new
clip-off threshold may then be entered.
6.13 Local reset of total display:
‘LOC. rSEt’
When activated this function enables the operator
to reset the BA338C total display to zero in the
display mode by operating the Up and Down push-
buttons simultaneously for more than two seconds.
To check the status of the local reset function
select 'LOC.rSEt' from the menu and press P
which will reveal if the function is 'On' or 'OFF'. If
necessary press the Up or Down button to change
the setting, followed by the E button to return to the
main menu.
The total display may also be remotely reset by
connecting terminals 7 and 8 together for more
than one second. See sections 4.2.6 and 4.3.6 of
this manual.
